1. Field of the Invention
The present invention relates to lead alloys. These are particularly useful in electric storage batteries in particular for use in the production of cast grids or other support structures for the active material of the electrodes which may be fabricated for such uses by conventional processes such as rolling. The invention is also applicable to electrodes for use in electrolysis cells.
The alloys are also applicable to electrodes in electrolysis cells for producing chemicals, electrowinning and electro-refining of metals, plating baths, to sheathing and cladding to protect articles such as cable and chemical plant and can be fabricated for such uses by conventional processes such as casting, extrusion and rolling.
2. The State of the Prior Art
The specification of British Pat. No. 712798 discloses lead-calcium and lead-tin-calcium alloys containing aluminium as an antidrossing agent. The presence of aluminium reduces the oxidation rate of the bulk of the molten metal and minimizes the loss of alloying element.
This earlier specification discloses an alloy containing 0.08% by weight calcium, 1.5% by weight tin, 0.05% by weight aluminium and 98.37% by weight lead. It also teaches that alloys having 0.03% to 0.1% calcium, 1% to 2% by weight tin, 0.01% to 0.1% aluminium, balance being lead and impurities, have superior properties. We have found however that at calcium contents below 0.075% the material is insufficiently hard within acceptable periods of time to be mechanically trimmed and in addition the corrosion of the alloy is greater as the tin content increases above 1%.
Lead-tin-calcium alloys have many excellent properties for use in electric storage battery electrodes but they suffer from reluctance to recharge and this is referred to as poor rechargeability.